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      </a></span></div></div> <div data-v-7dd95ae2><div data-v-7dd95ae2><main class="page" style="padding-right:0;"><section style="display:;"><div class="page-title"><h1 class="title">2-4 网页特效</h1> <div data-v-8a445198><i class="iconfont reco-account" data-v-8a445198><span data-v-8a445198>hasak</span></i> <i class="iconfont reco-date" data-v-8a445198><span data-v-8a445198>6/24/2022</span></i> <!----> <i class="tags iconfont reco-tag" data-v-8a445198><span class="tag-item" data-v-8a445198>JS</span></i></div></div> <div class="theme-reco-content content__default"><h1 id="_2-4-网页特效"><a href="#_2-4-网页特效" class="header-anchor">#</a> 2-4 网页特效</h1> <h2 id="一、pc-端网页特效"><a href="#一、pc-端网页特效" class="header-anchor">#</a> 一、PC 端网页特效</h2> <h3 id="_1-元素偏移量-offset-系列"><a href="#_1-元素偏移量-offset-系列" class="header-anchor">#</a> 1 元素偏移量 offset 系列</h3> <p><code>offset</code>翻译过来就是偏移量，我们使用 offset 系列相关属性可以动态的得到该元素的位置（偏移）、大小等</p> <ul><li>获得元素距离带有定位父元素的位置</li> <li>获得元素自身的大小（宽度高度）</li></ul> <p><strong>注意：返回的数值都不带单位</strong></p> <p><img src="https://hasakwebblogimg.oss-cn-hangzhou.aliyuncs.com/202211190942465.png" alt="image.png"></p> <img src="https://hasakwebblogimg.oss-cn-hangzhou.aliyuncs.com/202211190942323.png" alt="image.png" style="zoom:80%;"> <h3 id="offset-与-style-区别"><a href="#offset-与-style-区别" class="header-anchor">#</a> offset 与 style 区别</h3> <p><img src="https://hasakwebblogimg.oss-cn-hangzhou.aliyuncs.com/202211190943830.png" alt="image.png"></p> <h2 id="_2-元素可视区-client-系列"><a href="#_2-元素可视区-client-系列" class="header-anchor">#</a> 2 元素可视区 client 系列</h2> <p><code>client</code>翻译过来就是客户端，我们使用 client 系列的相关属性来获取元素可视区的相关信息。通过 client 系列的相关属性可以动态的得到该元素的边框大小、元素大小等。</p> <p><img src="https://hasakwebblogimg.oss-cn-hangzhou.aliyuncs.com/202211190943691.png" alt="image.png"></p> <img src="https://hasakwebblogimg.oss-cn-hangzhou.aliyuncs.com/202211190943903.png" alt="image.png" style="zoom:80%;"> <p><strong>案例： 淘宝 flexible.js 源码分析</strong></p> <h3 id="立即执行函数"><a href="#立即执行函数" class="header-anchor">#</a> 立即执行函数</h3> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token punctuation">(</span><span class="token keyword">function</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
<span class="token function">或者</span>
<span class="token punctuation">(</span><span class="token keyword">function</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span><span class="token punctuation">}</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br></div></div><p>主要作用：创建一个独立的作用域，避免了命名冲突问题</p> <div class="language-HTML line-numbers-mode"><pre class="language-html"><code><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>script</span><span class="token punctuation">&gt;</span></span><span class="token script"><span class="token language-javascript">
  <span class="token comment">// 1.立即执行函数: 不需要调用，立马能够自己执行的函数</span>
  <span class="token keyword">function</span> <span class="token function">fn</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token punctuation">}</span>
  <span class="token function">fn</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">;</span>

  <span class="token comment">// 2. 写法 也可以传递参数进来</span>
  <span class="token comment">// 1.(function() {})()    或者  2. (function(){}());</span>
  <span class="token punctuation">(</span><span class="token keyword">function</span><span class="token punctuation">(</span><span class="token parameter">a<span class="token punctuation">,</span> b</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>a <span class="token operator">+</span> b<span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">var</span> num <span class="token operator">=</span> <span class="token number">10</span><span class="token punctuation">;</span>
  <span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">(</span><span class="token number">1</span><span class="token punctuation">,</span> <span class="token number">2</span><span class="token punctuation">)</span><span class="token punctuation">;</span> <span class="token comment">// 第二个小括号可以看做是调用函数</span>
  
  <span class="token punctuation">(</span><span class="token keyword">function</span> <span class="token function">sum</span><span class="token punctuation">(</span><span class="token parameter">a<span class="token punctuation">,</span> b</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span>a <span class="token operator">+</span> b<span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token keyword">var</span> num <span class="token operator">=</span> <span class="token number">10</span><span class="token punctuation">;</span> <span class="token comment">// 局部变量</span>
  <span class="token punctuation">}</span><span class="token punctuation">(</span><span class="token number">2</span><span class="token punctuation">,</span> <span class="token number">3</span><span class="token punctuation">)</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span></span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>script</span><span class="token punctuation">&gt;</span></span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br></div></div><h3 id="pageshow"><a href="#pageshow" class="header-anchor">#</a> pageshow</h3> <p>下面三种情况都会刷新页面都会触发 load 事件</p> <ol><li>a 标签的超链接</li> <li>F5或者刷新按钮（强制刷新）</li> <li>前进后退按钮</li></ol> <p>但是火狐中，有个特点，有个“往返缓存”，这个缓存中不仅保存着页面数据，还保存了DOM和JavaScript的状态；实际上是将整个页面都保存在了内存里，所以此时后退按钮不能刷新页面。
此时可以使用<code>pageshow</code> 事件来触发，这个事件在页面显示时触发，无论页面是否来自缓存。在重新加载页面中，<code>pageshow</code> 会在 load 事件触发后触发；根据事件对象中的 persisted 来判断是否是缓存中的页面触发的<code>pageshow</code> 事件，注意这个事件给window添加。</p> <h2 id="_3-元素滚动-scroll-系列"><a href="#_3-元素滚动-scroll-系列" class="header-anchor">#</a> 3 元素滚动 scroll 系列</h2> <p><code>scroll</code> 翻译过来就是滚动的，我们使用 scroll 系列的相关属性可以动态的得到该元素的大小、滚动距离等。</p> <p><img src="https://hasakwebblogimg.oss-cn-hangzhou.aliyuncs.com/202211190945510.png" alt="image.png"></p> <p>如果浏览器的高（或宽）度不足以显示整个页面时，会自动出现滚动条。当滚动条向下滚动时，页面上面被隐藏掉的高度，我们就称为页面被卷去的头部。滚动条在滚动时会触发<code>onscroll</code>事件。</p> <p><img src="https://hasakwebblogimg.oss-cn-hangzhou.aliyuncs.com/202211190945544.png" alt="image.png"></p> <p><strong>案例：仿淘宝固定右侧侧边栏</strong></p> <ol><li><p>原先侧边栏是绝对定位</p></li> <li><p>当页面滚动到一定位置，侧边栏改为固定定位</p></li> <li><p>页面继续滚动，会让 返回顶部显示出来</p></li></ol> <p><strong>案例分析</strong></p> <ol><li><p>需要用到页面滚动事件 scroll  因为是页面滚动，所以事件源是 document</p></li> <li><p>滚动到某个位置，就是判断页面被卷去的上部值。</p></li> <li><p><strong>页面被卷去的头部：可以通过window.pageYOffset获得</strong>  如果是被卷去的左侧 window.pageXOffset</p></li> <li><p>注意，元素被卷去的头部是 <strong>element.scrollTop</strong>  , 如果是页面被卷去的头部 则是 <strong>window.pageYOffset</strong></p></li> <li><p>其实这个值 可以通过盒子的 offsetTop可以得到，如果大于等于这个值，就可以让盒子固定定位了</p></li></ol> <div class="language-HTML line-numbers-mode"><pre class="language-html"><code><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>style</span><span class="token punctuation">&gt;</span></span><span class="token style"><span class="token language-css">
  <span class="token selector">.slider-bar</span> <span class="token punctuation">{</span><span class="token property">position</span><span class="token punctuation">:</span> absolute<span class="token punctuation">;</span><span class="token property">left</span><span class="token punctuation">:</span> 50%<span class="token punctuation">;</span><span class="token property">top</span><span class="token punctuation">:</span> 300px<span class="token punctuation">;</span><span class="token property">margin-left</span><span class="token punctuation">:</span> 600px<span class="token punctuation">;</span>
    <span class="token property">width</span><span class="token punctuation">:</span> 45px<span class="token punctuation">;</span><span class="token property">height</span><span class="token punctuation">:</span> 130px<span class="token punctuation">;</span><span class="token property">background-color</span><span class="token punctuation">:</span> pink<span class="token punctuation">;</span><span class="token punctuation">}</span>
  <span class="token selector">.w</span> <span class="token punctuation">{</span><span class="token property">width</span><span class="token punctuation">:</span> 1200px<span class="token punctuation">;</span><span class="token property">margin</span><span class="token punctuation">:</span> 10px auto<span class="token punctuation">;</span><span class="token punctuation">}</span>
  <span class="token selector">.header</span> <span class="token punctuation">{</span><span class="token property">height</span><span class="token punctuation">:</span> 150px<span class="token punctuation">;</span><span class="token property">background-color</span><span class="token punctuation">:</span> purple<span class="token punctuation">;</span><span class="token punctuation">}</span>
  <span class="token selector">.banner</span> <span class="token punctuation">{</span><span class="token property">height</span><span class="token punctuation">:</span> 250px<span class="token punctuation">;</span><span class="token property">background-color</span><span class="token punctuation">:</span> skyblue<span class="token punctuation">;</span><span class="token punctuation">}</span>
  <span class="token selector">.main</span> <span class="token punctuation">{</span><span class="token property">height</span><span class="token punctuation">:</span> 1000px<span class="token punctuation">;</span><span class="token property">background-color</span><span class="token punctuation">:</span> yellowgreen<span class="token punctuation">;</span><span class="token punctuation">}</span>
  <span class="token selector">span</span> <span class="token punctuation">{</span><span class="token property">display</span><span class="token punctuation">:</span> none<span class="token punctuation">;</span><span class="token property">position</span><span class="token punctuation">:</span> absolute<span class="token punctuation">;</span><span class="token property">bottom</span><span class="token punctuation">:</span> 0<span class="token punctuation">;</span><span class="token punctuation">}</span>
</span></span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>style</span><span class="token punctuation">&gt;</span></span>

<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>div</span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">&quot;</span>slider-bar<span class="token punctuation">&quot;</span></span><span class="token punctuation">&gt;</span></span>
  <span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>span</span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">&quot;</span>goBack<span class="token punctuation">&quot;</span></span><span class="token punctuation">&gt;</span></span>返回顶部<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>span</span><span class="token punctuation">&gt;</span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>div</span><span class="token punctuation">&gt;</span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>div</span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">&quot;</span>header w<span class="token punctuation">&quot;</span></span><span class="token punctuation">&gt;</span></span>头部区域<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>div</span><span class="token punctuation">&gt;</span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>div</span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">&quot;</span>banner w<span class="token punctuation">&quot;</span></span><span class="token punctuation">&gt;</span></span>banner区域<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>div</span><span class="token punctuation">&gt;</span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>div</span> <span class="token attr-name">class</span><span class="token attr-value"><span class="token punctuation attr-equals">=</span><span class="token punctuation">&quot;</span>main w<span class="token punctuation">&quot;</span></span><span class="token punctuation">&gt;</span></span>主体部分<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>div</span><span class="token punctuation">&gt;</span></span>

<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>script</span><span class="token punctuation">&gt;</span></span><span class="token script"><span class="token language-javascript">
  <span class="token comment">//1. 获取元素</span>
  <span class="token keyword">var</span> sliderbar <span class="token operator">=</span> document<span class="token punctuation">.</span><span class="token function">querySelector</span><span class="token punctuation">(</span><span class="token string">'.slider-bar'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token keyword">var</span> banner <span class="token operator">=</span> document<span class="token punctuation">.</span><span class="token function">querySelector</span><span class="token punctuation">(</span><span class="token string">'.banner'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token comment">// banner.offestTop 就是被卷去头部的大小 一定要写到滚动的外面</span>
  <span class="token keyword">var</span> bannerTop <span class="token operator">=</span> banner<span class="token punctuation">.</span>offsetTop
  <span class="token comment">// 当我们侧边栏固定定位之后应该变化的数值</span>
  <span class="token keyword">var</span> sliderbarTop <span class="token operator">=</span> sliderbar<span class="token punctuation">.</span>offsetTop <span class="token operator">-</span> bannerTop<span class="token punctuation">;</span>
  <span class="token comment">// 获取main 主体元素</span>
  <span class="token keyword">var</span> main <span class="token operator">=</span> document<span class="token punctuation">.</span><span class="token function">querySelector</span><span class="token punctuation">(</span><span class="token string">'.main'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token keyword">var</span> goBack <span class="token operator">=</span> document<span class="token punctuation">.</span><span class="token function">querySelector</span><span class="token punctuation">(</span><span class="token string">'.goBack'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token keyword">var</span> mainTop <span class="token operator">=</span> main<span class="token punctuation">.</span>offsetTop<span class="token punctuation">;</span>
  
  <span class="token comment">// 2. 页面滚动事件 scroll</span>
  document<span class="token punctuation">.</span><span class="token function">addEventListener</span><span class="token punctuation">(</span><span class="token string">'scroll'</span><span class="token punctuation">,</span> <span class="token keyword">function</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token comment">// 3 .当我们页面被卷去的头部大于等于了 172 此时 侧边栏就要改为固定定位</span>
    <span class="token keyword">if</span> <span class="token punctuation">(</span>window<span class="token punctuation">.</span>pageYOffset <span class="token operator">&gt;=</span> bannerTop<span class="token punctuation">)</span> <span class="token punctuation">{</span>
      sliderbar<span class="token punctuation">.</span>style<span class="token punctuation">.</span>position <span class="token operator">=</span> <span class="token string">'fixed'</span><span class="token punctuation">;</span>
      sliderbar<span class="token punctuation">.</span>style<span class="token punctuation">.</span>top <span class="token operator">=</span> sliderbarTop <span class="token operator">+</span> <span class="token string">'px'</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span>
      sliderbar<span class="token punctuation">.</span>style<span class="token punctuation">.</span>position <span class="token operator">=</span> <span class="token string">'absolute'</span><span class="token punctuation">;</span>
      sliderbar<span class="token punctuation">.</span>style<span class="token punctuation">.</span>top <span class="token operator">=</span> <span class="token string">'300px'</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
    <span class="token comment">// 4. 当我们页面滚动到main盒子，就显示 goback模块</span>
    <span class="token keyword">if</span> <span class="token punctuation">(</span>window<span class="token punctuation">.</span>pageYOffset <span class="token operator">&gt;=</span> mainTop<span class="token punctuation">)</span> <span class="token punctuation">{</span>
      goBack<span class="token punctuation">.</span>style<span class="token punctuation">.</span>display <span class="token operator">=</span> <span class="token string">'block'</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span> <span class="token keyword">else</span> <span class="token punctuation">{</span>
      goBack<span class="token punctuation">.</span>style<span class="token punctuation">.</span>display <span class="token operator">=</span> <span class="token string">'none'</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
  <span class="token punctuation">}</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span></span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>script</span><span class="token punctuation">&gt;</span></span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br><span class="line-number">20</span><br><span class="line-number">21</span><br><span class="line-number">22</span><br><span class="line-number">23</span><br><span class="line-number">24</span><br><span class="line-number">25</span><br><span class="line-number">26</span><br><span class="line-number">27</span><br><span class="line-number">28</span><br><span class="line-number">29</span><br><span class="line-number">30</span><br><span class="line-number">31</span><br><span class="line-number">32</span><br><span class="line-number">33</span><br><span class="line-number">34</span><br><span class="line-number">35</span><br><span class="line-number">36</span><br><span class="line-number">37</span><br><span class="line-number">38</span><br><span class="line-number">39</span><br><span class="line-number">40</span><br><span class="line-number">41</span><br><span class="line-number">42</span><br><span class="line-number">43</span><br><span class="line-number">44</span><br><span class="line-number">45</span><br><span class="line-number">46</span><br><span class="line-number">47</span><br><span class="line-number">48</span><br></div></div><p><strong>页面被卷去的头部兼容性解决方案</strong>
需要注意的是，页面被卷去的头部，有兼容性问题，因此被卷去的头部通常有如下几种写法：</p> <ul><li>声明了 DTD，使用 document.documentElement.scrollTop</li> <li>未声明 DTD，使用  document.body.scrollTop</li> <li>新方法 window.pageYOffset 和 window.pageXOffset，IE9开始支持</li></ul> <div class="language-javascript line-numbers-mode"><pre class="language-javascript"><code><span class="token keyword">function</span> <span class="token function">getScroll</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
  <span class="token keyword">return</span> <span class="token punctuation">{</span>
    <span class="token literal-property property">left</span><span class="token operator">:</span> window<span class="token punctuation">.</span>pageXOffset <span class="token operator">||</span> document<span class="token punctuation">.</span>documentElement<span class="token punctuation">.</span>scrollLeft <span class="token operator">||</span> document<span class="token punctuation">.</span>body<span class="token punctuation">.</span>scrollLeft<span class="token operator">||</span> <span class="token number">0</span><span class="token punctuation">,</span>
    <span class="token literal-property property">top</span><span class="token operator">:</span> window<span class="token punctuation">.</span>pageYOffset <span class="token operator">||</span> document<span class="token punctuation">.</span>documentElement<span class="token punctuation">.</span>scrollTop <span class="token operator">||</span> document<span class="token punctuation">.</span>body<span class="token punctuation">.</span>scrollTop <span class="token operator">||</span> <span class="token number">0</span>
  <span class="token punctuation">}</span><span class="token punctuation">;</span>
<span class="token punctuation">}</span> 
使用的时候  <span class="token function">getScroll</span><span class="token punctuation">(</span><span class="token punctuation">)</span><span class="token punctuation">.</span>left
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br></div></div><h2 id="_4-三大系列总结"><a href="#_4-三大系列总结" class="header-anchor">#</a> 4 三大系列总结</h2> <p><img src="https://hasakwebblogimg.oss-cn-hangzhou.aliyuncs.com/202211190947526.png" alt="image.png"></p> <img src="https://hasakwebblogimg.oss-cn-hangzhou.aliyuncs.com/202211190947467.png" alt="image.png" style="zoom:67%;"> <img src="https://hasakwebblogimg.oss-cn-hangzhou.aliyuncs.com/202211190947438.png" alt="image.png" style="zoom:67%;"> <p><img src="https://hasakwebblogimg.oss-cn-hangzhou.aliyuncs.com/202211190947474.png" alt="image.png"></p> <p>他们主要用法：</p> <ol><li>offset系列经常用于获得元素位置 <code>offsetLeft</code> <code>offsetTop</code></li> <li>client 经常用于获取元素大小  <code>clientWidth</code> <code>clientHeight</code></li> <li>scroll经常用于获取滚动距离  <code>ScrollTop</code> <code>scrollLeft</code></li> <li>注意页面滚动的距离通过 <code>window.pageXOffset</code> 获得</li></ol> <h2 id="_5-mouseenter和mouseover的区别"><a href="#_5-mouseenter和mouseover的区别" class="header-anchor">#</a> 5 mouseenter和mouseover的区别</h2> <p>当鼠标移动到元素上时就会触发 <code>mouseenter</code>事件，类似 <code>mouseover</code>，它们两者之间的差别是</p> <ul><li><code>mouseover</code> 鼠标经过自身盒子会触发，经过子盒子还会触发</li> <li><code>mouseenter</code> 只会经过自身盒子触发</li> <li>之所以这样，因为<code>mouseenter</code> 不会冒泡，跟 <code>mouseenter</code> 搭配的鼠标离开 <code>mouseleave</code>同样不会冒泡</li></ul> <h2 id="_6-动画函数封装"><a href="#_6-动画函数封装" class="header-anchor">#</a> 6 动画函数封装</h2> <p><strong>核心原理：==通过定时器 setInterval() 不断移动盒子位置==</strong> <strong>实现步骤</strong></p> <ol><li>获得盒子当前位置</li> <li>让盒子在当前位置加上1个移动距离</li> <li>利用定时器不断重复这个操作</li> <li>加一个结束定时器的条件
注意此元素需要添加定位，才能使用element.style.left</li></ol> <div class="language-html line-numbers-mode"><pre class="language-html"><code><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>style</span><span class="token punctuation">&gt;</span></span><span class="token style"><span class="token language-css">
  <span class="token selector">div</span> <span class="token punctuation">{</span><span class="token property">position</span><span class="token punctuation">:</span> absolute<span class="token punctuation">;</span><span class="token property">left</span><span class="token punctuation">:</span> 0<span class="token punctuation">;</span><span class="token property">width</span><span class="token punctuation">:</span> 100px<span class="token punctuation">;</span><span class="token property">height</span><span class="token punctuation">:</span> 100px<span class="token punctuation">;</span><span class="token property">background-color</span><span class="token punctuation">:</span> pink<span class="token punctuation">;</span><span class="token punctuation">}</span>
</span></span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>style</span><span class="token punctuation">&gt;</span></span>

<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>div</span><span class="token punctuation">&gt;</span></span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>div</span><span class="token punctuation">&gt;</span></span>

<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>script</span><span class="token punctuation">&gt;</span></span><span class="token script"><span class="token language-javascript">
  <span class="token comment">// 动画原理</span>
  <span class="token comment">// 1. 获得盒子当前位置  </span>
  <span class="token comment">// 2. 让盒子在当前位置加上1个移动距离</span>
  <span class="token comment">// 3. 利用定时器不断重复这个操作</span>
  <span class="token comment">// 4. 加一个结束定时器的条件</span>
  <span class="token comment">// 5. 注意此元素需要添加定位，才能使用element.style.left</span>
  <span class="token keyword">var</span> div <span class="token operator">=</span> document<span class="token punctuation">.</span><span class="token function">querySelector</span><span class="token punctuation">(</span><span class="token string">'div'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token keyword">var</span> timer <span class="token operator">=</span> <span class="token function">setInterval</span><span class="token punctuation">(</span><span class="token keyword">function</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token keyword">if</span> <span class="token punctuation">(</span>div<span class="token punctuation">.</span>offsetLeft <span class="token operator">&gt;=</span> <span class="token number">400</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
      <span class="token comment">// 停止动画 本质是停止定时器</span>
      <span class="token function">clearInterval</span><span class="token punctuation">(</span>timer<span class="token punctuation">)</span><span class="token punctuation">;</span>
    <span class="token punctuation">}</span>
    div<span class="token punctuation">.</span>style<span class="token punctuation">.</span>left <span class="token operator">=</span> div<span class="token punctuation">.</span>offsetLeft <span class="token operator">+</span> <span class="token number">1</span> <span class="token operator">+</span> <span class="token string">'px'</span><span class="token punctuation">;</span>
  <span class="token punctuation">}</span><span class="token punctuation">,</span> <span class="token number">30</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
</span></span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>script</span><span class="token punctuation">&gt;</span></span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br><span class="line-number">20</span><br><span class="line-number">21</span><br><span class="line-number">22</span><br></div></div><p><strong>动画函数简单封装</strong></p> <ul><li><p>注意函数需要传递2个参数，<strong>动画对象</strong>和<strong>移动到的距离</strong></p> <p><strong>动画函数给不同元素记录不同定时器</strong></p></li> <li><p>如果多个元素都使用这个动画函数，每次都要 var 声明定时器。我们可以给不同的元素使用不同的定时器（自己专门用自己的定时器）。</p></li> <li><p>核心原理：利用 JS 是一门动态语言，可以很方便的给当前对象添加属性</p></li></ul> <div class="language-html line-numbers-mode"><pre class="language-html"><code><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>style</span><span class="token punctuation">&gt;</span></span><span class="token style"><span class="token language-css">
  <span class="token selector">div</span> <span class="token punctuation">{</span><span class="token property">position</span><span class="token punctuation">:</span> absolute<span class="token punctuation">;</span><span class="token property">left</span><span class="token punctuation">:</span> 0<span class="token punctuation">;</span><span class="token property">width</span><span class="token punctuation">:</span> 100px<span class="token punctuation">;</span><span class="token property">height</span><span class="token punctuation">:</span> 100px<span class="token punctuation">;</span><span class="token property">background-color</span><span class="token punctuation">:</span> pink<span class="token punctuation">;</span><span class="token punctuation">}</span>
  <span class="token selector">span</span> <span class="token punctuation">{</span><span class="token property">position</span><span class="token punctuation">:</span> absolute<span class="token punctuation">;</span><span class="token property">left</span><span class="token punctuation">:</span> 0<span class="token punctuation">;</span><span class="token property">top</span><span class="token punctuation">:</span> 200px<span class="token punctuation">;</span><span class="token property">display</span><span class="token punctuation">:</span> block<span class="token punctuation">;</span>
    <span class="token property">width</span><span class="token punctuation">:</span> 150px<span class="token punctuation">;</span><span class="token property">height</span><span class="token punctuation">:</span> 150px<span class="token punctuation">;</span><span class="token property">background-color</span><span class="token punctuation">:</span> purple<span class="token punctuation">;</span><span class="token punctuation">}</span>
</span></span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>style</span><span class="token punctuation">&gt;</span></span>

<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>button</span><span class="token punctuation">&gt;</span></span>点击夏雨荷才走<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>button</span><span class="token punctuation">&gt;</span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>div</span><span class="token punctuation">&gt;</span></span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>div</span><span class="token punctuation">&gt;</span></span>
<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>span</span><span class="token punctuation">&gt;</span></span>夏雨荷<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>span</span><span class="token punctuation">&gt;</span></span>

<span class="token tag"><span class="token tag"><span class="token punctuation">&lt;</span>script</span><span class="token punctuation">&gt;</span></span><span class="token script"><span class="token language-javascript">
  <span class="token comment">// var obj = {};</span>
  <span class="token comment">// obj.name = 'andy';</span>
  <span class="token comment">// 简单动画函数封装obj目标对象 target 目标位置</span>
  <span class="token comment">// 给不同的元素指定了不同的定时器</span>
  <span class="token keyword">function</span> <span class="token function">animate</span><span class="token punctuation">(</span><span class="token parameter">obj<span class="token punctuation">,</span> target</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token comment">// 当我们不断的点击按钮，这个元素的速度会越来越快，因为开启了太多的定时器</span>
    <span class="token comment">// 解决方案就是 让我们元素只有一个定时器执行</span>
    <span class="token comment">// 先清除以前的定时器，只保留当前的一个定时器执行</span>
    <span class="token function">clearInterval</span><span class="token punctuation">(</span>obj<span class="token punctuation">.</span>timer<span class="token punctuation">)</span><span class="token punctuation">;</span>
    obj<span class="token punctuation">.</span>timer <span class="token operator">=</span> <span class="token function">setInterval</span><span class="token punctuation">(</span><span class="token keyword">function</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
      <span class="token keyword">if</span> <span class="token punctuation">(</span>obj<span class="token punctuation">.</span>offsetLeft <span class="token operator">&gt;=</span> target<span class="token punctuation">)</span> <span class="token punctuation">{</span>
        <span class="token comment">// 停止动画 本质是停止定时器</span>
        <span class="token function">clearInterval</span><span class="token punctuation">(</span>obj<span class="token punctuation">.</span>timer<span class="token punctuation">)</span><span class="token punctuation">;</span>
      <span class="token punctuation">}</span>
      obj<span class="token punctuation">.</span>style<span class="token punctuation">.</span>left <span class="token operator">=</span> obj<span class="token punctuation">.</span>offsetLeft <span class="token operator">+</span> <span class="token number">1</span> <span class="token operator">+</span> <span class="token string">'px'</span><span class="token punctuation">;</span>

    <span class="token punctuation">}</span><span class="token punctuation">,</span> <span class="token number">30</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token punctuation">}</span>

  <span class="token keyword">var</span> div <span class="token operator">=</span> document<span class="token punctuation">.</span><span class="token function">querySelector</span><span class="token punctuation">(</span><span class="token string">'div'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token keyword">var</span> span <span class="token operator">=</span> document<span class="token punctuation">.</span><span class="token function">querySelector</span><span class="token punctuation">(</span><span class="token string">'span'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token keyword">var</span> btn <span class="token operator">=</span> document<span class="token punctuation">.</span><span class="token function">querySelector</span><span class="token punctuation">(</span><span class="token string">'button'</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token comment">// 调用函数</span>
  <span class="token function">animate</span><span class="token punctuation">(</span>div<span class="token punctuation">,</span> <span class="token number">300</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
  btn<span class="token punctuation">.</span><span class="token function">addEventListener</span><span class="token punctuation">(</span><span class="token string">'click'</span><span class="token punctuation">,</span> <span class="token keyword">function</span><span class="token punctuation">(</span><span class="token punctuation">)</span> <span class="token punctuation">{</span>
    <span class="token function">animate</span><span class="token punctuation">(</span>span<span class="token punctuation">,</span> <span class="token number">200</span><span class="token punctuation">)</span><span class="token punctuation">;</span>
  <span class="token punctuation">}</span><span class="token punctuation">)</span>
</span></span><span class="token tag"><span class="token tag"><span class="token punctuation">&lt;/</span>script</span><span class="token punctuation">&gt;</span></span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br><span class="line-number">19</span><br><span class="line-number">20</span><br><span class="line-number">21</span><br><span class="line-number">22</span><br><span class="line-number">23</span><br><span class="line-number">24</span><br><span class="line-number">25</span><br><span class="line-number">26</span><br><span class="line-number">27</span><br><span class="line-number">28</span><br><span class="line-number">29</span><br><span class="line-number">30</span><br><span class="line-number">31</span><br><span class="line-number">32</span><br><span class="line-number">33</span><br><span class="line-number">34</span><br><span class="line-number">35</span><br><span class="line-number">36</span><br><span class="line-number">37</span><br><span class="line-number">38</span><br><span class="line-number">39</span><br></div></div></div></section> <footer class="page-edit"><!----> <!----></footer> <div class="page-nav"><p class="inner"><span class="prev"><a href="/blogs/基础/js/20221114js09.html" class="prev">
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